The response of adult and free-living stages of Necator americanus, in vitro, to anthelmintics.

The in vitro response of adults (males and females) and free-living stages of Necator americanus one of the human hookworms, to a wide variety of 20 broad and narrow spectrum anthelmintics was tested. Almost all the broad spectrum anthelmintics influenced males, females and free-living stages at different levels and showed good activity with EC50 values varying from about 0.0002 and 0.0007 mg/l for pyrantel pamoate and tricofenol piperazine respectively to about 8.47 and 7.6 mg/l for morantel tartrate and amoscanate respectively. Certain drugs (emetine, praziquantel and suramin) exerted their effect either on male or female or free-living stages at 10.0 mg/l level. It is concluded that either sex or life-cycle stage alone may not be an effective criteria for screening of anthelmintics which have been employed at large; and females of nematodes (in particular those of N. americanus) should be taken into account for proposing EC50 as they were found to require relatively highest EC50 level in almost all the instances studied presently.